A variety of different types of excavation machines have been developed for cutting drifts, tunnels, subterranean roadways and the like in which a rotatable head is mounted on an arm that is in turn movably mounted at a main frame so as to create a desired tunnel cross sectional profile. WO2012/156841, WO 2012/156842, WO 2010/050872, WO 2012/156884, WO2011/093777, DE 20 2011 050 143U1. All described apparatus for mill cutting of rock and minerals in which a rotating cutting head forced into contact with the rock face as supported by a movable arm. In particular, WO 2012/156884 describes the cutting end of the machine in which the rotatable heads are capable of being raised and lowered vertically and deflecting in the lateral sideways direction by a small angle in an attempt to try enhance the cutting action.
WO 2014/090589 describes a machine for digging roadways tunnels and the like in which a plurality of cutting heads are movable to dig into the rock face via a pivoting arcuate cutting path. US 2003/0230925 describes a rock excavator having a cutter head mounting a plurality of annular disc cutters suitable to operate in an undercutting mode.
Furthermore, it has been observed that conventional cutting machines are not optimised to cut hard rock having a strength typically beyond 120 MPa whilst creating a tunnel or subterranean cavity safely and reliably of desired cross sectional configuration. Accordingly, what is required is a cutting machine that addresses these problems.
It has been observed that clearing the floor of the tunnel from detached rock material requires a considerable amount of time and can lead to a delay in the tunnel generating process. Further, the floor clearing operation needs to be carried out carefully and thoroughly, since the floor of the tunnel is used by various other parts of the cutting apparatus for support purposes.
Known cutting units for the use with a cutting apparatus suitable for creating tunnels or subterranean roadway comprise a cutting arm configured for pivotal movement around at least one pivot axis and a cutting head mounted to the cutting arm. The cutting head comprises a rotatable cutting element for detaching material from the rock face.
The detached material accumulates on the floor of the tunnel and needs to be removed before the cutting apparatus can move forward in order to proceed with detaching material from the rock face.
From GB 2 153 876 A a clearing arrangement is known, which is mounted to the cutting arm. The clearing arrangement comprises a clearing blade for pushing detached rock material in the direction of a transfer conveyor for transferring the detached material away from the working area.
However, the front edge of the clearing blades of the known cutting units are spaced from the front edge of the cutting head in order to prevent that the clearing blade interferes with an obstacle in the rock face such as protruding rock material not yet being detached by means of the cutting element.
Due to the distance that known clearing blades have with respect to the rock face and to the front edge of the cutting head, such clearing blades cannot be used for scraping loose material from the rock face after material has been detached by means of the cutting elements of the cutting head. Further, the distance between the front edge of the clearing blade and the rock face leads to the fact that only a small amount of the detached and accumulated rock material on the floor of the tunnel is pushed in direction of the transport conveyor resulting in a time consuming and effortful clearing operation.